diff --git a/packages/react-client/src/ReactFlightReplyClient.js b/packages/react-client/src/ReactFlightReplyClient.js
index 18fc2834e1d..742655486dd 100644
--- a/packages/react-client/src/ReactFlightReplyClient.js
+++ b/packages/react-client/src/ReactFlightReplyClient.js
@@ -112,6 +112,7 @@ function escapeStringValue(value: string): string {
 
 export function processReply(
   root: ReactServerValue,
+  formFieldPrefix: string,
   resolve: (string | FormData) => void,
   reject: (error: mixed) => void,
 ): void {
@@ -171,7 +172,7 @@ export function processReply(
             // $FlowFixMe[incompatible-type] We know it's not null because we assigned it above.
             const data: FormData = formData;
             // eslint-disable-next-line react-internal/safe-string-coercion
-            data.append('' + promiseId, partJSON);
+            data.append(formFieldPrefix + promiseId, partJSON);
             pendingParts--;
             if (pendingParts === 0) {
               resolve(data);
@@ -268,7 +269,7 @@ export function processReply(
         // The reference to this function came from the same client so we can pass it back.
         const refId = nextPartId++;
         // eslint-disable-next-line react-internal/safe-string-coercion
-        formData.set('' + refId, metaDataJSON);
+        formData.set(formFieldPrefix + refId, metaDataJSON);
         return serializeServerReferenceID(refId);
       }
       throw new Error(
@@ -308,7 +309,7 @@ export function processReply(
     resolve(json);
   } else {
     // Otherwise, we use FormData to let us stream in the result.
-    formData.set('0', json);
+    formData.set(formFieldPrefix + '0', json);
     if (pendingParts === 0) {
       // $FlowFixMe[incompatible-call] this has already been refined.
       resolve(formData);
diff --git a/packages/react-server-dom-webpack/src/ReactFlightDOMClientBrowser.js b/packages/react-server-dom-webpack/src/ReactFlightDOMClientBrowser.js
index f847a636e6c..c835d0b81d7 100644
--- a/packages/react-server-dom-webpack/src/ReactFlightDOMClientBrowser.js
+++ b/packages/react-server-dom-webpack/src/ReactFlightDOMClientBrowser.js
@@ -124,7 +124,7 @@ function encodeReply(
   string | URLSearchParams | FormData,
 > /* We don't use URLSearchParams yet but maybe */ {
   return new Promise((resolve, reject) => {
-    processReply(value, resolve, reject);
+    processReply(value, '', resolve, reject);
   });
 }
 
diff --git a/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js b/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
index d549c10693c..777e4271e6e 100644
--- a/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
+++ b/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
@@ -22,8 +22,6 @@ import {
 import {
   createResponse,
   close,
-  resolveField,
-  resolveFile,
   getRoot,
 } from 'react-server/src/ReactFlightReplyServer';
 
@@ -79,20 +77,12 @@ function decodeReply<T>(
   body: string | FormData,
   webpackMap: ServerManifest,
 ): Thenable<T> {
-  const response = createResponse(webpackMap);
   if (typeof body === 'string') {
-    resolveField(response, 0, body);
-  } else {
-    // $FlowFixMe[prop-missing] Flow doesn't know that forEach exists.
-    body.forEach((value: string | File, key: string) => {
-      const id = +key;
-      if (typeof value === 'string') {
-        resolveField(response, id, value);
-      } else {
-        resolveFile(response, id, value);
-      }
-    });
+    const form = new FormData();
+    form.append('0', body);
+    body = form;
   }
+  const response = createResponse(webpackMap, '', body);
   close(response);
   return getRoot(response);
 }
diff --git a/packages/react-server-dom-webpack/src/ReactFlightDOMServerEdge.js b/packages/react-server-dom-webpack/src/ReactFlightDOMServerEdge.js
index d549c10693c..777e4271e6e 100644
--- a/packages/react-server-dom-webpack/src/ReactFlightDOMServerEdge.js
+++ b/packages/react-server-dom-webpack/src/ReactFlightDOMServerEdge.js
@@ -22,8 +22,6 @@ import {
 import {
   createResponse,
   close,
-  resolveField,
-  resolveFile,
   getRoot,
 } from 'react-server/src/ReactFlightReplyServer';
 
@@ -79,20 +77,12 @@ function decodeReply<T>(
   body: string | FormData,
   webpackMap: ServerManifest,
 ): Thenable<T> {
-  const response = createResponse(webpackMap);
   if (typeof body === 'string') {
-    resolveField(response, 0, body);
-  } else {
-    // $FlowFixMe[prop-missing] Flow doesn't know that forEach exists.
-    body.forEach((value: string | File, key: string) => {
-      const id = +key;
-      if (typeof value === 'string') {
-        resolveField(response, id, value);
-      } else {
-        resolveFile(response, id, value);
-      }
-    });
+    const form = new FormData();
+    form.append('0', body);
+    body = form;
   }
+  const response = createResponse(webpackMap, '', body);
   close(response);
   return getRoot(response);
 }
diff --git a/packages/react-server-dom-webpack/src/ReactFlightDOMServerNode.js b/packages/react-server-dom-webpack/src/ReactFlightDOMServerNode.js
index 98d4291de98..dc78f9a28eb 100644
--- a/packages/react-server-dom-webpack/src/ReactFlightDOMServerNode.js
+++ b/packages/react-server-dom-webpack/src/ReactFlightDOMServerNode.js
@@ -30,7 +30,6 @@ import {
   reportGlobalError,
   close,
   resolveField,
-  resolveFile,
   resolveFileInfo,
   resolveFileChunk,
   resolveFileComplete,
@@ -88,10 +87,9 @@ function decodeReplyFromBusboy<T>(
   busboyStream: Busboy,
   webpackMap: ServerManifest,
 ): Thenable<T> {
-  const response = createResponse(webpackMap);
+  const response = createResponse(webpackMap, '');
   busboyStream.on('field', (name, value) => {
-    const id = +name;
-    resolveField(response, id, value);
+    resolveField(response, name, value);
   });
   busboyStream.on('file', (name, value, {filename, encoding, mimeType}) => {
     if (encoding.toLowerCase() === 'base64') {
@@ -101,8 +99,7 @@ function decodeReplyFromBusboy<T>(
           'the wrong assumption, we can easily fix it.',
       );
     }
-    const id = +name;
-    const file = resolveFileInfo(response, id, filename, mimeType);
+    const file = resolveFileInfo(response, name, filename, mimeType);
     value.on('data', chunk => {
       resolveFileChunk(response, file, chunk);
     });
@@ -123,20 +120,12 @@ function decodeReply<T>(
   body: string | FormData,
   webpackMap: ServerManifest,
 ): Thenable<T> {
-  const response = createResponse(webpackMap);
   if (typeof body === 'string') {
-    resolveField(response, 0, body);
-  } else {
-    // $FlowFixMe[prop-missing] Flow doesn't know that forEach exists.
-    body.forEach((value: string | File, key: string) => {
-      const id = +key;
-      if (typeof value === 'string') {
-        resolveField(response, id, value);
-      } else {
-        resolveFile(response, id, value);
-      }
-    });
+    const form = new FormData();
+    form.append('0', body);
+    body = form;
   }
+  const response = createResponse(webpackMap, '', body);
   close(response);
   return getRoot(response);
 }
diff --git a/packages/react-server/src/ReactFlightReplyServer.js b/packages/react-server/src/ReactFlightReplyServer.js
index a39ccb91bae..f74d1c06769 100644
--- a/packages/react-server/src/ReactFlightReplyServer.js
+++ b/packages/react-server/src/ReactFlightReplyServer.js
@@ -131,6 +131,8 @@ Chunk.prototype.then = function <T>(
 
 export type Response = {
   _bundlerConfig: ServerManifest,
+  _prefix: string,
+  _formData: FormData,
   _chunks: Map<number, SomeChunk<any>>,
   _fromJSON: (key: string, value: JSONValue) => any,
 };
@@ -309,7 +311,17 @@ function getChunk(response: Response, id: number): SomeChunk<any> {
   const chunks = response._chunks;
   let chunk = chunks.get(id);
   if (!chunk) {
-    chunk = createPendingChunk(response);
+    const prefix = response._prefix;
+    const key = prefix + id;
+    // Check if we have this field in the backing store already.
+    const backingEntry = response._formData.get(key);
+    if (backingEntry != null) {
+      // We assume that this is a string entry for now.
+      chunk = createResolvedModelChunk(response, (backingEntry: any));
+    } else {
+      // We're still waiting on this entry to stream in.
+      chunk = createPendingChunk(response);
+    }
     chunks.set(id, chunk);
   }
   return chunk;
@@ -452,10 +464,16 @@ function parseModelString(
   return value;
 }
 
-export function createResponse(bundlerConfig: ServerManifest): Response {
+export function createResponse(
+  bundlerConfig: ServerManifest,
+  formFieldPrefix: string,
+  backingFormData?: FormData = new FormData(),
+): Response {
   const chunks: Map<number, SomeChunk<any>> = new Map();
   const response: Response = {
     _bundlerConfig: bundlerConfig,
+    _prefix: formFieldPrefix,
+    _formData: backingFormData,
     _chunks: chunks,
     _fromJSON: function (this: any, key: string, value: JSONValue) {
       if (typeof value === 'string') {
@@ -470,19 +488,24 @@ export function createResponse(bundlerConfig: ServerManifest): Response {
 
 export function resolveField(
   response: Response,
-  id: number,
-  model: string,
+  key: string,
+  value: string,
 ): void {
-  const chunks = response._chunks;
-  const chunk = chunks.get(id);
-  if (!chunk) {
-    chunks.set(id, createResolvedModelChunk(response, model));
-  } else {
-    resolveModelChunk(chunk, model);
+  // Add this field to the backing store.
+  response._formData.append(key, value);
+  const prefix = response._prefix;
+  if (key.startsWith(prefix)) {
+    const chunks = response._chunks;
+    const id = +key.substr(prefix.length);
+    const chunk = chunks.get(id);
+    if (chunk) {
+      // We were waiting on this key so now we can resolve it.
+      resolveModelChunk(chunk, value);
+    }
   }
 }
 
-export function resolveFile(response: Response, id: number, file: File): void {
+export function resolveFile(response: Response, key: string, file: File): void {
   throw new Error('Not implemented.');
 }
 
@@ -490,7 +513,7 @@ export opaque type FileHandle = {};
 
 export function resolveFileInfo(
   response: Response,
-  id: number,
+  key: string,
   filename: string,
   mime: string,
 ): FileHandle {